This is the first renewal of a Program Project that has been in effect for two years. It was originally submitted in order to study the molecular related to a number of devastating human conditions which have as their central feature an association with the with the major histocompatibility complex. Three investigators who have worked on both independent and collaborating projects relate to both clinical manifestations and such as insulin dependent diabetes mellitus and allergies as well as to basic 1-1. of T cell recognition and cellular proliferation wish to continue their integrated approach to these various human diseases. As previously, central core facilities are requested in order to centralize resources and technology and to more efficiently utilize personnel and funds. Each of the individual projects follows directly from the laboratory to the clinic and back to the research laboratory and should provide important insights into the pathogenesis of human disease.